Democrat Jim Martin is campaigning feverishly, aided by Barack Obama’s grass-roots organization from the presidential race and a flood of support from the national party, but he remains an underdog against incumbent Republican Sen. Saxby Chambliss in a Georgia runoff election considered pivotal for the balance of power in the U.S. Senate.

Mr. Martin is behind in polls, has half the cash of his opponent and early-voting turnout among black voters is stagnating - a crucial block for any Democrat in this mostly conservative state where Republicans also hold the other U.S. Senate seat, the governor’s office and majorities in both houses of the state General Assembly.

That doesn’t bode well for Mr. Martin and Senate Democrats eyeing an unexpected victory Tuesday to put them one vote away from a filibuster-breaking 60-vote majority and the power to ram the party’s agenda through the chamber.

“The holiday, the cold weather, the relatively lackluster campaign [by Mr. Martin] will put Senator Chambliss in the winning column,” said University of Georgia political science professor Audrey A. Haynes. “With all of the potential issues that are positive for Martin and negative for Chambliss, it should be a Martin win, albeit a bit of a squeaker. But there just doesn’t seem to be any fire.”

Mr. Martin balked at the charge he was not exciting the electorate.

“I don’t think that’s true,” he told The Washington Times. “We are working hard at it. You know, it is not for me to excite them. They are excited about this race. They are excited about change in this country. They are excited about my candidacy … and the issues I’ve talked about. That’s what’s exciting.”

Most of the excitement has surrounded Mr. Martin’s events that were headlined by celebrity politicians, including a visit last week by former President Clinton and a fundraiser Sunday in Atlanta with climate-change crusader and former Vice President Al Gore.

Both campaigns overhauled their get-out-the-vote drives to counter the voter fatigue typical in runoffs. But Mr. Martin needs more of a turnout boost than his opponent. He finished nearly 110,000 votes behind Mr. Chambliss in the general election, despite the enthusiasm generated by Mr. Obama at the top of the Democratic ticket.

The task only gets more difficult in this second round of balloting, which was triggered when none of the contenders captured more than 50 percent of the vote Nov. 4.

Mr. Martin enlisted Mr. Obama’s turnout team from Georgia and neighboring states. They have opened about 25 office across the state with 200 staff members and thousands of volunteers, supplying Mr. Obama’s database from the general election to target voters for Mr. Martin.

“We have Georgians,” Chambliss campaign spokeswoman Michelle Grasso said. “We don’t need the AFL-CIO or people from other states.”

Mr. Chambliss finished first in the general election 49.8 percent to Mr. Martin’s 46.8 percent. Libertarian Allen Buckley, a tax lawyer from Smyrna, Ga., took 3.4 percent of the vote to help force a runoff. Under Georgia law, only the top two candidates advance to the Tuesday vote.

Mr. Martin continues to trail in polls and even his campaign staff say their own pollsters show the former state lawmaker behind 48 percent to 46 percent, though within the margin of error.

A new poll released Monday showed Mr. Chambliss widening his lead to a six-point margin since the general election. The survey by Public Policy Polling, a nonpartisan firm based in Raleigh, N.C., found the incumbent gaining among independent voters that likely backed Mr. Buckley in the first vote.

The poll also gauged declining interest among black voters and young voters. Those groups likely benefited Mr. Martin as they helped give Mr. Obama 47 percent of the vote in a solid red state won by Republican presidential nominee Sen. John McCain with 52.2 percent.

“They may have voted for Jim Martin as long as they were at the polls, but for now anyway, it doesn’t look like they’re planning to come out just for Martin,” Public Policy Polling president Dean Debnam said. “That puts Saxby Chambliss in good shape headed to the final week of the campaign.”

Martin supporters hold out hope Mr. Obama will swoop in to rally the base, but those chances appear to be dimming, as the president-elect would risk suffering a political loss before the inauguration and expose himself to criticism of striking a partisan tone during what he promises will be a transition to a postpartisan Washington.

Mr. Obama did produce a radio spot for the Democrat that is airing around the state, and there are reports a TV ad featuring Mr. Obama may be in the works.

Even without a TV appearance or an in-person visit, Mr. Obama looms large in the election.

Mr. Obama echoes the Obama presidential campaign, calling for change and blasting Mr. Chambliss for siding with Wall Street over Main Street. He blames him for the financial meltdown and for voting for the $700 billion rescue for the finance industry.

“For six years, he voted to get us into this mess,” said the baritone narrator in a frequently aired Martin TV ad.

But Mr. Chambliss, the National Republican Senatorial Committee and some third-party groups are dominating the TV ad war. The ads hit Mr. Martin for being soft on crime, for supporting abortions for children without parental consent and for backing tax increases as a state representative while voting to increase his own taxpayer-funded expense account.